It’s disputed whether anything is de re necessary, or whether all things are contingent.

Essence: the essence of a thing is what makes it the thing it is. It’s part of the essence of de re necessary things to exist.

If God is de re necessary, it doesn’t make sense to ask what caused God.

Kant: existence isn’t a predicate.

A priori and a posteriori arguments

Cosmological (and most other arguments for the existence of God) are a posteriori. They argue from experience, are inductive rather than deductive, and can be denied without irrationality.

The Ontological argument is unusual in being a priori. It’s a deductive argument that claims that the very definition of God requires that God must exist. If it succeeds, it is irrational not to believe in the existence of God.

The Monologium: An example of a Meditation on the Grounds of Faith. A Soliloquy

Not addressed to believers, so its success depends on convincing atheists.

An a posteriori, inductive argument – an early version of Aquinas’s 4th way (“From grades of perfection in things”).

We all agree on the ordering of men according to how just they are. Claims to arbitrariness are refuted by treating the sceptic unjustly and seeing if he complains.

What is the source of these common judgements? The concept JUSTICE is well-defined and society-independent. It’s not a Humpty-Dumpty word that means what any individual likes.

We understand justice through justice itself. We’re talking about justice itself and not a concept.

We recognise goodness or justice not through good or just things/acts themselves, but though a being that is good/just “through itself” and through whom other things inherit their goodness/justice. This implies a priori knowledge of justice, and a Platonic world-view: but with perfect ideas in the mind of God rather than Forms.

This sorting process applies to all goods that we rank, and there must be the same source of the ability, namely God. And the source of the good must itself be most excellently good1 – and so on for other attributes – that than which no greater can be conceived.

The Proslogium: Faith Seeking Understanding. A Discourse

I believe that I may understand.

The Proslogium is an explication of what is believed, not a proof of what is believed. The reason for this belief was given a posteriori in the Monologium. The Proslogium is addressed to believers.

We all have a shared concept of God as “that than which no greater can be conceived”. By thinking on what this means, only the fool would fail to agree that God must exist, because existence is implied by the meaning of the concept

The proof of this is:-1. God is that than which no greater can be conceived, a concept understood by believers and non-believers.2. Concepts can exist in the mind alone, or both in the mind and in reality. 3. It is greater to exist both in the mind and in reality than in the mind alone.4. Therefore God must exist in reality as well as in the mind. If God didn’t exist in reality, we could conceive of one who did, who would be greater than God.

So, its only failure to think through the concept GOD that allows one to imagine his non-existence.

The deductive form of the argument is:-1. That than which no greater can be conceived includes the feature of existence. 2. God is that than which no greater can be conceived 3. Therefore, God exists.

Gaunilo

Claimed that there was a problem with the form of the argument, because if we apply it to the greatest possible island, that too must exist. Anselm claims in response that God is a special case.

Gaunilo’s second claim is that no-one can understand God (ie. we don’t possess the concept). Anselm’s response is similar to the argument in the Monologium – we can ascend from the good things we know to the source of the good. Also, existence is something that can be known.

St. Thomas Aquinas

Agrees with Gaunilo’s second objection – we don’t have a shared definition of God.

Claims that we can know God’s essence, and that therefore we can see that existence is part of that essence, and that therefore God must exist.

God is unique in that his essence includes existence.

Descartes is right that once you understand the concept of God, then God must exist. But it’s only true that if there is a God, then God exists. Note2.

Kant

Objected to the second premise of one formulation of Descartes’ argument¸ namely:-2. It is of the essence of God that he exists, for by definition God’s essence is to exist.

Against this:-1. God is defined mostly in negative terms, and we have no clear idea3 of a necessary being. 2. The only sort of necessity is of analytic statements, true in virtue of the way language is used. It is ridiculous to use deductive logic in support of an existence claim. For reality, observation is required.

For Kant, existence is not a perfection or a predicate, nor is it part of anything’s essence. It is that in the absence of which there can be no perfections.

While it is true that all triangles have three angles4, there might yet be no triangles; as is demonstrated by the parallel case of unicorns and their horns.

Gerard Hughes claims that logic is agnostic about whether a necessary being must or cannot exist.

Others claim that some things can be shown be logic to exist – eg. the equator (according to Gareth Moore). It makes sense neither to look for it, nor to doubt5 it.

We need to distinguish words from concepts. The unbeliever grasps the word “God”, but does not grasp the concept, which includes necessary existence. But such a being as God isn’t of a continuum with other beings – so saying that God exists isn’t the same as saying that tame tigers exist.

So, Kant’s objection that existence isn’t a predicate may not be relevant, is the theist isn’t claiming that God is a thing with predicates.

Alvin Plantinga’s Reformulation of the argument

Plantinga firstly re-states in formal terms Anselm’s own argument. He does this as follows6:-

1. God exists in the understanding but not in reality. (Assumption for reductio)

2. Existence in reality is greater than existence in the understanding alone. (Premise)

3. A being having all of God's properties plus existence in reality can be conceived. (Premise)

4. A being having all of God's properties plus existence in reality is greater than God. (From (1) and (2).)

5. A being greater than God can be conceived. (From (3) and (4).)

6. It is false that a being greater than God can be conceived. (From definition of “God”.)

7. Hence, it is false that God exists in the understanding but not in reality. (From (1), (5), (6).)

8. God exists in the understanding. (Premise, to which even the Fool agrees.)

Footnote 1: I have a feeling there might be Third Man objections here. See The Third Man for my (very technical) BA-finals thoughts on this topic.

Footnote 2: Presumably what this is saying is that the correct concept of God cannot have him ceasing to exist in any way, assuming that he exists in the first place. But this still doesn’t imply that the concept GOD is instantiated.

Footnote 3: Descartes’ whole system depends on the cogency of our “clear and distinct” ideas. He ends in a circle, in that he needs God to underwrite this supposed fact (by being no deceiver, or not letting us go astray in what we most clearly and distinctly perceive), while one of his clear and distinct ideas is of God. Descartes thought he could clearly and distinctly conceive of mind independent of body (as does Plantinga, and as all dualists must), but this is (to say the least) hotly disputed. See The Real Distinction for my BA Finals essay on this topic.

Footnote 5: But surely this is a muddle? The equator is only defined as a mathematical abstraction, on the assumption that the earth is a perfect sphere, which it isn’t. Maybe, though, we could define the equator on the real earth as the locus of points equidistant from the poles. This wouldn’t be a circle, and might not even be well defined (do we count distance going up and down hills / waves?). Whatever, the equator isn’t a thing we can even in principle look for.